error[E0499]: cannot borrow `**other` as mutable more than once at a time
  --> $DIR/issue-46589.rs:23:21
   |
LL |         *other = match (*other).get_self() {
   |                        -------- first mutable borrow occurs here
LL |             Some(s) => s,
LL |             None => (*other).new_self()
   |                     ^^^^^^^^
   |                     |
   |                     second mutable borrow occurs here
   |                     first borrow later used here

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0499`.